I am sure that there are a lot of bad names registered for every hand full of great names.
In the past month i was going through deleted lists and saw an adult name related to babies or infants, i was like wtf. I guess some people will register anything if they could make a buck. I wasn't looking for adult names or anything, it just happened to be near some names that I was looking at on the lists.
I have had some bad ones, most often when I decide to register names after a long night of drinking ( early in my domaining career ). I had thought I got a great name only to look at it a little closer the next day and see I spelled wrong or it was just a crazy thought for a domain that nobody in the history of mankind will ever have again...LOL
I think many of these non-sensical names were registered to be used for criminal activities like spamming, viagra/zombie websites, doorways, and other stuffs.